Air-conditioning system

ABSTRACT

An air-conditioning system includes: a first duct through which air discharged from an electronic instrument passes; a water vapor retention chamber; an evaporator configured to be heated by the air passing through the first duct and thereby to generate water vapor inside the water vapor retention chamber; a desiccant rotor including an adsorbent to adsorb moisture and configured to be driven and rotated by a driving unit; a humidification chamber; a second duct configured to feed outdoor air introduced from an outdoor space into the humidification chamber; and a third duct configured to feed the air passing through the humidification chamber into a room where the electronic instrument is installed, wherein a portion of the desiccant rotor is located inside the water vapor retention chamber, and another portion of the desiccant rotor is located inside the humidification chamber.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of International Patent ApplicationNo. PCT/JP2010/065325 filed Sep. 7, 2010 and designated the U.S., theentire contents of which are incorporated herein by reference.

FIELD

The embodiments discussed herein relate to an air-conditioning systemconfigured to condition indoor air by introducing outdoor air.

BACKGROUND

In recent years, a large amount of data are being handled by computers(computer devices) with the advent of an advanced information society,and numerous computers are often installed in one room for the purposeof collective management in a facility such as a data center. Under thiscircumstance, the computers generate a large amount of heat which maylead to erroneous operations or failures. Accordingly, a measure forcooling the computers is used. For this reason, a data center is usuallydesigned to let the heat generated in the computers out of the computersusing fans (air blowers), and to adjust the temperature in the roomusing an air-conditioning machine (an air conditioner).

In the meantime, the amount of heat generated by the computersfluctuates depending on operating conditions of the computers. Aconceivable option for reliably preventing erroneous operations orfailures of the computers attributed to the heat is to use anair-conditioning machine, which has a cooling capacity corresponding toa sum of maximum amounts of heat generated by all the computers in acomputer room. However, an air-conditioning machine with such a largecooling capacity generally has large power consumption, which isundesirable in terms of energy conservation. In this regard, efficientoperation of an air-conditioning facility inclusive of anair-conditioning machine is preferred.

Patent Document 1: Japanese Laid-open Patent Publication No. 2010-32174

A conventional data center is designed to manage the air temperaturewhile circulating the air within a computer room. As a consequence, nomatter how efficiently the air-conditioning facility is operated, theair-conditioning facility consumes at least the electric powercorresponding to the amount of heat generated by all the computers inthe computer room, and may be unable to achieve further reduction of theabove-mentioned power consumption.

SUMMARY

According to an aspect, an air-conditioning system includes: a firstduct through which air discharged from an electronic instrument passes;a water vapor retention chamber; an evaporator configured to be heatedby the air passing through the first duct and thereby to generate watervapor inside the water vapor retention chamber; a desiccant rotorincluding an adsorbent to adsorb moisture and configured to be drivenand rotated by a driving unit; a humidification chamber; a second ductconfigured to feed outdoor air introduced from an outdoor space into thehumidification chamber; and a third duct configured to feed the airpassing through the humidification chamber into a room where theelectronic instrument is installed, wherein a portion of the desiccantrotor is located inside the water vapor retention chamber, and anotherportion of the desiccant rotor is located inside the humidificationchamber.

The object and advantages of the invention will be realized and attainedby means of the elements and combinations particularly pointed out inthe claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and arenot restrictive of the invention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram depicting an example of a computer room;

FIG. 2 is a schematic diagram of an air-conditioning system according toan embodiment;

FIG. 3 is a schematic diagram of a desiccant rotor device;

FIG. 4 is a schematic diagram (a perspective view) depicting anevaporator and its adjacent portions;

FIG. 5 is a flowchart for explaining an operation of theair-conditioning system according to the embodiment; and

FIG. 6 is a schematic diagram of an air-conditioning system of acomparative example, which is provided with a heating-type humidifier.

DESCRIPTION OF EMBODIMENTS

A prelude for facilitating the understanding of an embodiment will bedescribed below prior to explaining the embodiment.

In order to reduce power used for air conditioning in a facility such asa data center, outdoor air may be introduced into a room when thetemperature of the outdoor air is low. In the case of a data centerdesigned to supply the air adjusted to the temperature of 20° C. into aroom by using an air-conditioning machine, for example, reduction in thepower used for an air-conditioning facility may be expected byintroducing the outdoor air into the room when the temperature of theoutdoor air is equal to or below 20° C.

However, the humidity in the room is also managed in the data center inorder to prevent occurrence of troubles in the computers caused bystatic electricity. Even when the amount of moisture contained in theair is the same, the humidity (which hereinafter means the relativehumidity) of the air becomes lower as its temperature becomes higher.For this reason, if the outdoor air in the winter, such as the outdoorair having the temperature equal to or below 10° C. and the humidityequal to or below 50%, is directly introduced into a computer room, thehumidity falls to a low level along with the rise in temperature.

Generally, the humidity in the computer room is adjusted within a rangefrom about 50% to 60% in the data center by installing a heating-typehumidifier, an ultrasonic-type humidifier or the like in the room.However, simple introduction of the outdoor air into the computer roommay lead to a shortage of humidification capacity with only aconventionally used humidifier. Accordingly, a countermeasure such asincreasing in the number of humidifiers or introducing a humidifier witha larger humidification capacity becomes preferable. Nevertheless, powerconsumption will be increased by taking such a countermeasure. As aconsequence, the effect of reduction in the power consumption by theair-conditioning facility is not fully obtained even when the outdoorair is introduced.

In view of the above, there is a demand for an air-conditioning systemwhich takes less power for managing the humidity when the outdoor air isintroduced.

EMBODIMENT

FIG. 1 is a schematic diagram depicting an example of a computer room.The following embodiment describes air conditioning of a computer roomas an example.

A computer room 10 includes an instrument installation area 11 a whereracks 12 are installed, a free access floor 11 b provided under thefloor of the instrument installation area 11 a and having power cablesand signal cables installed, and an exhaust flow channel 11 c providedin the attic of the instrument installation area 11 a. A plurality ofcomputers (not depicted) are placed in each of the racks 12. Moreover,an air-conditioning machine 15 is installed in the computer room 10. Theair-conditioning machine 15 is configured to cool the air taken inthrough the exhaust flow channel 11 c, and to supply the cooled air tothe free access floor 11 b.

The racks 12 are arranged in rows. The racks 12 in one row and the racks12 in another row adjacent to the one row are laid out in such a mannerthat intake surfaces of the racks 12 in the one row face intake surfacesof the racks 12 in the other row or in such a manner that exhaustsurfaces of the racks 12 in the one row face exhaust surfaces of theracks 12 of the other row. In addition, an opening 14 for connecting theinstrument installation area 11 a to the exhaust flow channel 11 c isprovided at each portion on the ceiling near the exhaust surfaces of theracks 12, while a grille (a vent) 13 for connecting the instrumentinstallation area 11 a to the free access floor 11 b is provided at eachportion on the floor near the intake surfaces of the racks 12.

The low-temperature air supplied from the air-conditioning machine 15 tothe free access floor 11 b is sent to the instrument installation area11 a via the grilles 13 and is taken into the racks 12 from the intakesurfaces. Then, the air heated to a high temperature as a result ofcooling the computers is discharged from the exhaust surfaces of theracks 12. This air enters the exhaust flow channel 11 c via the openings14 and returns to the air-conditioning machine 15 through the exhaustflow channel 11 c.

FIG. 2 is a schematic diagram of an air-conditioning system according tothe embodiment.

As depicted in FIG. 2, the air-conditioning system according to theembodiment includes a humidity adjustment unit 20, ducts 21 to 28, airvalves 41 to 44, fans (air blowers) 46 to 48, and sensor units 51 and 52which detect the temperature and humidity. Meanwhile, the humidityadjustment unit 20 includes a water vapor retention chamber 20 a, ahumidification chamber 20 b, a desiccant rotor device 30, and anevaporator 35. The air-conditioning system according to the embodimentfurther includes a control device 50, which is configured to receivesignals from the sensor units 51 and 52 and to control drive of thedesiccant rotor device 30, the air valves 41 to 44, and the fans 46 to48.

As schematically depicted in FIG. 3, the desiccant rotor device 30includes a disk-shaped desiccant rotor 31, and a driving unit 32 locatedalong the central axis of the desiccant rotor 31 and configured torotate the desiccant rotor 31. The desiccant rotor 31 is formed of amember such as a non-woven fabric, which allows passage of the air inthe thickness direction thereof, and contains an adsorbent having aproperty to adsorb moisture in the air. Silica gel, zeolite, activatedcarbon, and the like may be used as the adsorbent. In this embodiment,activated carbon is used as the adsorbent because activated carbon maybe recovered (dried) at a relatively low temperature.

FIG. 4 is a schematic diagram (a perspective view) depicting theevaporator 35 and its adjacent portions. As depicted in FIG. 4, theevaporator 35 includes a heat transfer plate 38, a plurality of fins(heat-absorbing plates) 37 arranged on one side of the heat transferplate 38, and a water storage unit 36 arranged on the other side of theheat transfer plate 38. The heat transfer plate 38 and the fins 37 aremade of a material having fine heat conductivity such as copper (Cu),aluminum (Al) or carbon. Here, the heat transfer plate 38 and the fins37 are made of copper, and the fins 37 and the heat transfer plate 38are brazed to one another.

The water storage unit 36 is formed by containing a member having a finewater-absorbing property such as a non-woven fabric. When theair-conditioning system is in operation, water is supplied to the waterstorage unit 36 as appropriate through a water supply pipe 39 so thatthe water storage unit 36 is always kept in a wet condition. A portionof the evaporator 35 where the fins 37 are arranged will be hereinafterreferred to as a heat exchange unit and a portion of the evaporator 35where the water storage unit 36 is arranged will be hereinafter referredto as an evaporation unit.

Next, relations of connection among the humidity adjustment unit 20 andthe ducts 21 to 28 will be described with reference to FIG. 2. The duct21 (an example of a first duct), the water vapor retention chamber 20 aof the humidity adjustment unit 20, and the duct 23 are linearlyarranged and connected in this order. Meanwhile, the duct 22 isconnected to an end of the duct 21 near the water vapor retentionchamber 20 a in a perpendicular manner to the duct 21. In thisembodiment, both of the duct 21 and the duct 23 are connected to theexhaust flow channel 11 c of the computer room 10 while the duct 22 isconnected outdoors.

The fan 46 is located inside the duct 21. The air at a relatively hightemperature (from 30° C. to 35° C., for example) passing through theexhaust flow channel 11 c of the computer room 10 is introduced into theduct 21 by rotation of this fan 46. Meanwhile, the heat exchange unit(the fins 37) of the evaporator 35 is located at an end portion insidethe duct 21 near the water vapor retention chamber 20 a. The airintroduced into the duct 21 moves to the duct 22 through spaces formedbetween the fins 37 of the evaporator 35 and is then dischargedoutdoors. The air valve 41 is located inside the duct 22.

The air valve 42 is located at a junction of the water vapor retentionchamber 20 a and the duct 21 while the air valve 43 is located at ajunction of the water vapor retention chamber 20 a and the duct 23. Theinside of the water vapor retention chamber 20 a becomes a substantiallyenclosed space when both of the air valves 42 and 43 are closed.

The evaporation unit (the water storage unit 36) of the evaporator 35 islocated inside the water vapor retention chamber 20 a. The evaporationunit is thermally connected to the heat exchange unit (the fins 37)inside the duct 21 via the heat transfer plate 38 which passes through agap provided below the air valve 42. In addition, a portion of thedesiccant rotor device 30 above the driving unit 32 is located insidethe water vapor retention chamber 20 a as depicted in FIG. 2.

The duct 24 (an example of a fourth duct), the humidification chamber 20b of the humidity adjustment unit 20, and the duct 25 (an example of athird duct) are linearly arranged and connected in this order, and arelocated below the duct 21, the water vapor retention chamber 20 a, andthe duct 23. In this embodiment, both of the duct 24 and the duct 25 areconnected to the exhaust flow channel 11 c in the computer room 10.

The fan 47 (an example of a second flow rate adjustment unit) is locatedinside the duct 24. The air in the computer room 10 is introduced intothe duct 24 by rotation of this fan 47. A portion of the desiccant rotordevice 30 below the driving unit 32 is located inside the humidificationchamber 20 b. The air passing through the desiccant rotor device 30 isreleased into the computer room 10 via the duct 25.

The fan 48 (an example of a first flow rate adjustment unit) is locatedinside the duct 26 (an example of a second duct). The outdoor air isintroduced into the duct 26 by rotation of this fan 48. This duct 26 isconnected to the duct 25 via the duct 28, and is also connected to theduct 24 via the duct 27. The air valve (a switch valve) 44 is located ata branching portion between the duct 27 and the duct 28. The airintroduced into the duct 26 is sent either to the duct 27 or to the duct28 by means of this air valve 44.

The sensor unit 51 is located inside the duct 26 and is configured todetect the temperature and humidity of the outdoor air. Meanwhile, thesensor unit 52 is located inside the duct 25 and is configured to detectthe temperature and humidity of the air passing through the duct 25.

Next, an operation of the desiccant rotor device 30 of this embodimentwill be described.

As mentioned previously, the air valves 42 and 43 are provided at thetwo end portions of the water vapor retention chamber 20 a, and theinside of the water vapor retention chamber 20 a becomes thesubstantially enclosed space when both of the air valves 42 and 43 areclosed. When the fins 37 of the evaporator 35 are heated by therelatively high-temperature air passing through the ducts 21 and 22, theheat of the fins 37 is also transferred to the water storage unit 36located inside the water vapor retention chamber 20 a, whereby themoisture evaporates from the water storage unit 36. Accordingly, both ofthe temperature and the moisture (a relative vapor pressure) inside thewater vapor retention chamber 20 a are increased. As a consequence, alarge amount of moisture is adsorbed to the desiccant rotor 31.

This desiccant rotor 31 is driven and rotated by the driving unit 32.When the portion of the desiccant rotor 31 having absorbed the moisturegoes into the humidification chamber 20 b, the moisture evaporates fromthe desiccant rotor 31 because the air entering the humidificationchamber 20 b has the relatively low humidity. Thus, the desiccant rotor31 is recovered (dried) and the amount of moisture contained in the airpassing through the desiccant rotor 31 is increased as a consequence.

Assuming that a rotational speed of the desiccant rotor 31 remainswithin a predetermined range, the faster the rotational speed of thedesiccant rotor 31 is, the larger the amount of moisture contained inthe air passing through the desiccant rotor 31 is. Thus, the amount ofhumidification may be adjusted by the rotational speed of the desiccantrotor 31. Although FIG. 2 depicts the case where the desiccant rotordevice 30 has the single desiccant rotor 31, a plurality of thedesiccant rotors 31 may be placed in the humidity adjustment unit 20 ifthe single desiccant rotor 31 does not achieve a sufficient amount ofhumidification.

An operation of the air-conditioning system according to this embodimentwill be described below with reference to a flowchart in FIG. 5. Here,both of the air valves 42 and 43 are closed while the air valve 41 isopen in an initial state.

First, in step S11, the control device 50 acquires detection results ofa temperature T_(out) of the outdoor air and a humidity M_(out) of theoutdoor air from the sensor unit 51. Then, in step S12, the controldevice 50 determines whether or not the temperature T_(out) of theoutdoor air is equal to or below a preset temperature T₁ which is set inadvance. When the temperature T_(out) of the outdoor air is determinedto be higher than the preset temperature T₁ (such as 25° C.) (in thecase of NO), the outdoor air is not taken into the computer room 10. Inthis case, the operation goes back from step S12 to step S11.

On the other hand, when the temperature T_(out) of the outdoor air isdetermined to be equal or below the preset temperature T₁ (in the caseof YES) in step S12, the operation goes to step S13. Then, in step S13,the control device 50 determines whether or not the humidity M_(out) ofthe outdoor air is equal to or above a preset humidity M₁ such as aweight absolute humidity of 0.099 (kg/kg (DA)).

When the humidity M_(out) of the outdoor air is determined to be higherthan the preset value M₁ (in the case of YES), this means thathumidification is not preferable. In this case, the operation goes tostep S14 in which the control device 50 drives the air valve 44 so as toclose the duct 27 side and to open the duct 28 side. Further, in orderto discharge the exhaust air in the same amount as the taken-in outdoorair from the computer room 10 to the outdoors, the control device 50drives the air valve 41 so as to open (continue to open) the duct 22.Thereafter, the operation goes to step S15 to rotate (start rotation orcontinue rotation of) the fans 46 and 48. Accordingly, the outdoor airpasses through the duct 26, the duct 28, and the duct 25 in this orderand is introduced into the computer room 10. In the meantime, theexhaust air is discharged from the computer room 10 through the ducts 21and 22. In other words, the outdoor air is introduced into the computerroom 10 without passing through the desiccant rotor 31 in this case.After the processing in step S14 and S15 is executed, the operationreturns to step S11.

If the fan 47 and the desiccant rotor 31 are rotated in step S17 to bedescribed later, then the rotation of the fan 47 and the desiccant rotor31 is stopped in step S15.

On the other hand, when the humidity M_(out) of the outdoor air isdetermined to be equal to or below the preset value M₁ (in the case ofNO) in step S13, this means that humidification is preferable whenintroducing the outdoor air. In this case, the operation goes to stepS16 in which the control device 50 drives the air valve 44 so as toclose the duct 28 side and to open the duct 27 side. Thereafter, theoperation goes to step S17 in which the control device 50 rotates(starts rotation or continues rotation of) the fans 46, 47, and 48, aswell as rotates (starts rotation or continues rotation of) the desiccantrotor 31.

Accordingly, the relatively high-temperature air (such as from 30° C. to35° C.) discharged from the racks 12 is introduced into the duct 21 andthe desiccant rotor 31 starts rotation at a preset rotational speed.Meanwhile, water is supplied to the evaporator (the water storage unit36) via the water supply pipe 39. Hence, the inside of the water vaporretention chamber 20 turns into the state of a high temperature and ahigh humidity, and a large amount of moisture is adsorbed to thedesiccant rotor 31. The moisture is carried to the humidificationchamber 20 b with rotation of the desiccant rotor 31.

In the meantime, the air in the computer room 10 is introduced into theduct 24 by rotation of the fan 47 while the outdoor air is introducedinto the duct 26 by rotation of the fan 48. These air components aremixed at the junction of the duct 24 and the duct 27 and go into thehumidification chamber 20 b of the humidity adjustment unit 20. Thehumidity of this mixed air is increased by receiving sufficient moisturewhen passing through the desiccant rotor 31 located in thehumidification chamber 20 b, and the mixed air is then introduced intothe computer room 10 via the duct 25. After the processing in step S16and S17 is executed, the operation goes to step S18.

In step S18, the control device 50 acquires detection results of thetemperature and humidity of the air, which passes through the duct 25,from the sensor unit 52. Then, the operation goes to step S19 in whichthe control device 50 controls the rotational speed of the desiccantrotor 31 or the rotational speed of the fan 47 on the basis of thehumidity of the air passing through the duct 25. Specifically, therotational speed of the desiccant rotor 31 is increased or therotational speed of the fan 47 is increased when the humidity of the airpassing through the duct 25 is lower than a preset range. On the otherhand, the rotational speed of the desiccant rotor 31 is reduced or therotational speed of the fan 47 is reduced when the humidity of the airpassing through the duct 25 is higher than the preset range. Then, theoperation returns to step S11 and the above-described processing isrepeated. This processing is repeatedly carried out until stopped by anoperator.

As described above, in this embodiment, the outdoor air is introducedinto the computer room 10 when the temperature of the outdoor air islow. In addition, when the humidity of the outdoor air is low, the airto be introduced into the computer room 10 is humidified with the watervapor generated by using the high-temperature air discharged from thecomputer room 10. This may make it possible to reduce loads on theair-conditioning machine 15 and the humidifier located in the computerroom 10, and thereby to bring about an effect that power used for airconditioning the computer room 10 may be reduced.

Here, it is preferable to dry the inside of the water vapor retentionchamber 20 a when the air-conditioning system is stopped for a longperiod. In the case of the air-conditioning system of this embodiment,the water vapor retention chamber 20 a may be dried by rotating the fan46 while opening the air valves 42 and 43 as well as closing the airvalve 41.

In the above-described embodiment, the outdoor air introduced throughthe duct 26 is mixed with the air in the computer room 10 introducedthrough the duct 24, and then the mixed air is supplied to the desiccantrotor device 30. Instead, the outdoor air may be supplied directly tothe desiccant rotor device 30. However, in the latter case, the amountof humidification is likely to be reduced because the air supplied tothe desiccant rotor device 30 has a low temperature. For this reason, itis preferable to mix the outdoor air with the air in the computer room10 and thereby to increase the temperature of the mixed air as in theabove-described embodiment.

Further, the mixing ratio between the air in the computer room 10introduced through the duct 24 and the outdoor air may be changeddepending on the temperature detected by the sensor unit 52.

A result of investigation of power consumption in the case of performinghumidification by using the desiccant rotor device and the case ofperforming humidification by using a heating-type humidifier will bedescribed below.

Example 1

The air-conditioning system depicted in FIG. 2 is constructed asExample 1. The desiccant rotor 31 has a diameter of 20 cm. Airtightnessof each of a space between a housing of the water vapor retentionchamber 20 a and the desiccant rotor 31 and a space between a housing ofthe humidification chamber 20 b and the desiccant rotor 31 is secured byusing a seal material (a packing) made of a fluororesin.

The desiccant rotor 31 employing a corrugated fin structure is used.Activated carbon in an amount of about 600 g, which is subjected to asurface treatment with nitric acid and thereby provided with ahydrophilic property, is filled as the adsorbent in the desiccant rotor31. The activated carbon has a grain size of about 500 μm.

Then, the air-conditioning system is operated when the outdoor air hasthe temperature of about 10° C. and the humidity of about 35%. At thistime, the air introduced from the computer room 10 into the ducts 21 and24 has the temperature of about 35° C. and the humidity of about 28%.Meanwhile, the air prepared by mixing the air in the computer room 10with the outdoor air at a volume ratio of 1:1 is supplied to thehumidification chamber 20 b at a flow rate of 1 m³/min.

The temperature of the air after passing through the desiccant rotor 31is measured with the sensor unit 52 inside the duct 25, and the numbersof revolutions of the desiccant rotor device 30 and the fans 46 to 48are controlled in such a manner as to set the temperature of the airflowing in the duct 25 equal to 20° C. and to set the humidity thereofequal to 55%. Here, the number of revolutions of the desiccant rotor 31is set to 1 to 2 revolutions per minute.

In this case, the power consumption by the desiccant rotor device 30 isequal to 50 W while the power consumption by the fans 46 to 48 is equalto 120 W, and the total power consumption is equal to 170 W.

Example 2

An air-conditioning system is constructed in a similar manner to Example1 except that silica gel (manufactured by Fuji Silysia Chemical Ltd.) inan amount of 800 g is filled as the adsorbent in the desiccant rotor 31.In addition, similarly to Example 1, the temperature of the air afterpassing through the desiccant rotor 31 is measured with the sensor unit52 inside the duct 25, and the numbers of revolutions of the desiccantrotor device 30 and the fans 46 to 48 are controlled in such a manner asto set the temperature of the air flowing in the duct 25 equal to 20° C.and to set the humidity thereof equal to 55%. Here, the number ofrevolutions of the desiccant rotor 31 is set to 1 revolution per minute.

In this case, the power consumption by the desiccant rotor device 30 isequal to 60 W while the power consumption by the fans 46 to 48 is equalto 120 W, and the total power consumption is equal to 180 W.

Comparative Example

A heating-type humidifier 63 is located inside a duct 61 as depicted inFIG. 6. Relatively high-temperature air is introduced from a computerroom into the duct 61 by a fan 64, and humidified air is released in thecomputer room from the opposite side. Here, the heating-type humidifier63 includes a non-woven fabric, a water supply pipe configured to supplywater to the non-woven fabric, and an electric heater configured to heatthe non-woven fabric.

A duct 62 is connected to a halfway portion (downstream of theheating-type humidifier 63) of the duct 61. Outdoor air is introducedfrom the outdoors into this duct 62 by a fan 65. In addition, a sensorunit 66 configured to detect the temperature and humidity of the airpassing through the duct 61 is located at an outlet side of the duct 61.

Using the air-conditioning system depicted in FIG. 6, the numbers ofrevolutions of the fans 64 and 65 are controlled in such a manner as toset a volume ratio between the air introduced from the computer roominto the duct 61 and the air (the outdoor air) introduced from theoutdoors into the duct 62 equal to 1:1. As a result, the temperature ofthe air discharged from the duct 61 is set equal to 20° C. and thehumidity thereof is set equal to 50%. In this case, the total powerconsumption by the heating-type humidifier 63 (the heater) and the fans64 and 65 is equal to 350 W.

From Examples 1 and 2 as well as Comparative Example described above,the power reduction effect of the air-conditioning systems according tothe embodiment is successfully confirmed.

It is to be noted that the technique disclosed in the above-describedembodiment is not limited only to an air-conditioning system for airconditioning a computer room, but may be also applicable to airconditioning in a room where an electronic instrument other than acomputer is installed.

All examples and conditional language recited herein are intended forthe pedagogical purposes of aiding the reader in understanding theinvention and the concepts contributed by the inventor to further theart, and are not to be construed as limitations to such specificallyrecited examples and conditions, nor does the organization of suchexamples in the specification relate to a showing of the superiority andinferiority of the invention. Although one or more embodiments of thepresent invention have been described in detail, it should be understoodthat the various changes, substitutions, and alterations could be madehereto without departing from the spirit and scope of the invention.

What is claimed is:
 1. An air-conditioning system comprising: a firstduct through which air discharged from an electronic instrument passes;a water vapor retention chamber; an evaporator configured to be heatedby the air passing through the first duct and thereby to generate watervapor inside the water vapor retention chamber; a desiccant rotorincluding an adsorbent to adsorb moisture and configured to be drivenand rotated by a driving unit; a humidification chamber; a second ductconfigured to feed outdoor air introduced from an outdoor space into thehumidification chamber; and a third duct configured to feed the airpassing through the humidification chamber into a room where theelectronic instrument is installed, wherein a portion of the desiccantrotor is located inside the water vapor retention chamber, and anotherportion of the desiccant rotor is located inside the humidificationchamber.
 2. The air-conditioning system according to claim 1, furthercomprising: a fourth duct to which air in the room where the electronicinstrument is installed is introduced, wherein the air prepared bymixing the outdoor air introduced through the second duct with the airintroduced through the fourth duct is supplied to the humidificationchamber.
 3. The air-conditioning system according to claim 2, furthercomprising: a first flow rate adjustment unit capable of adjusting aflow rate of the outdoor air to be introduced into the second duct; anda second flow rate adjustment unit capable of adjusting a flow rate ofthe air to be introduced into the fourth duct.
 4. The air-conditioningsystem according to claim 2, further comprising: a fifth duct directlyconnecting the second duct to the third duct, wherein a switch valveconfigured to switch a direction of flow of the outdoor air introducedinto the second duct to any one of a direction toward the humidificationchamber and a direction toward the fifth duct is provided at a junctionof the second duct and the fifth duct.
 5. The air-conditioning systemaccording to claim 1, the evaporator includes: a heat-absorbing platelocated in the first duct; and a water storage unit located in the watervapor retention chamber and thermally connected to the heat-absorbingplate.
 6. The air-conditioning system according to claim 1, furthercomprising: a sensor unit configured to detect a humidity of the airpassing through the third duct; and a control device configured tocontrol a rotational speed of the desiccant rotor in accordance with ahumidity detection result obtained by the sensor unit.
 7. Theair-conditioning system according to claim 1, wherein activated carbonis contained in the desiccant rotor.
 8. The air-conditioning systemaccording to claim 1, wherein an openable and closable air valve isprovided at each of two ends of the water vapor retention chamber. 9.The air-conditioning system according to claim 1, wherein the electronicinstrument is a computer.
 10. An air-conditioning system comprising: afirst duct through which air discharged from an electronic instrumentpasses; a water vapor retention chamber; an evaporator configured to beheated by the air passing through the first duct and thereby to generatewater vapor inside the water vapor retention chamber; a desiccant rotorincluding an adsorbent to adsorb moisture and configured to be drivenand rotated by a driving unit; a humidification chamber; a second ductconfigured to feed outdoor air introduced from an outdoor space into thehumidification chamber; a third duct configured to feed the air passingthrough the humidification chamber into a room where the electronicinstrument is installed; a fourth duct connected to the second duct andconfigured to supply air in the room where the electronic instrument isinstalled to the humidification chamber; a fifth duct directlyconnecting the second duct to the third duct; a first flow rateadjustment unit capable of adjusting a flow rate of the air to beintroduced into the second duct; a second flow rate adjustment unitcapable of adjusting a flow rate of the air to be introduced into thefourth duct; a switch valve located at a junction of the second duct andthe fifth duct and configured to switch a direction of flow of theoutdoor air introduced into the second duct to any one of a directiontoward the humidification chamber and a direction toward the fifth duct;a first sensor unit configured to detect a temperature and a humidity ofthe outdoor air; a second sensor unit configured to detect a temperatureand a humidity of the air passing through the third duct; and a controldevice configured to control the first flow rate adjustment unit, thesecond flow rate adjustment unit, the switch valve, and the desiccantrotor in accordance with outputs from the first sensor unit and thesecond sensor unit, wherein a portion of the desiccant rotor is locatedinside the water vapor retention chamber, and another portion of thedesiccant rotor is located inside the humidification chamber.
 11. Ahumidifier comprising: an evaporator configured to generate water vaporby using waste heat; a desiccant rotor including an adsorbent to adsorbthe water vapor; and a humidification chamber configured to humidify airby using moisture adsorbed to the adsorbent.